Seals for annular spaces in downhole applications have to respond to a variety of changing conditions. During production, the produced fluids can raise operating temperatures to 350° F. or more. On the other hand, particularly in frigid climates and during shut in periods of no production, the surrounding temperature around a wellbore seal can plunge to 35° F. or even less. Traditional annular non-metallic seal designs employ anti-extrusion barriers on the top and the bottom. These devices or rings often follow the generally rectangular shape of the seal, when viewed in section. The backup rings have a generally U-shape and feature slight interference on the inside diameter and more significant interference on the outside diameter, as installed. An example of the generally U-shaped design for the anti-extrusion ring in an annular seal can be seen in U.S. Pat. No. 4,496,162. In a variation of this design, additional seal material has been added to the inside dimension of the seal assembly to make a portion of the seal protrude beyond the backup rings on the inside diameter dimension. Even though an increase in the inside diameter interference reduced failures at low temperatures, the prior design proved unreliable in exposure to even colder temperatures as experienced in shut in conditions in the harshest cold climates. Additionally, the increase in inside diameter interference made the seal significantly more difficult to install. Compression packer seals are generally illustrated in U.S. Pat. Nos. 1,350,553; 3,229,767; 3,554,280 and 4,326,588.
In the present invention, installation interference that activates the seal is generated by the relaxed OD of the seal being larger than the OD of the annular gap the seal is being installed in and the relaxed ID of the seal being smaller than the ID of the annular gap the seal is being installed in. The seal does not rely of any external axial load to function. The seal is assisted by pressure during normal functionality.
Accordingly, the present invention presents improvements to seal design to handle the colder environments. In one feature, the backup ring design has been revised to allow it to act as a spring to promote its ability to act as an extrusion barrier. In another development, resilient ring seals have been placed in the seal body and dimensionally configured to be installed in their respective grooves with a residual stored force to promote the operation of the seal assembly in reduced temperature environments. These and other features of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.